At the present time, various types of displays are used, and the practical use of various types of displays is studied. All of these displays except for cathode-ray tube types aim at a reduction in thickness. Further, there is an-increasing demand for flexible types. To this end, studies have been made on the use of synthetic resin sheets or synthetic resin films instead of conventional glass substrates constituting displays. Furthermore, studies have also been made on display substrates that use a gas barrier film for external oxygen and water vapor shielding purposes.
In addition to mechanical strength, smoothness, gas barrier properties and the like, for example, heat resistance, moisture resistance and mechanical strength against heat, moisture and mechanical external force, for example, in the step of stacking various functional layers for imparting a function as a display to the synthetic resin film, or the step of forming a gas barrier layer for imparting gas barrier properties are required of synthetic resin films as a material for display substrates.
Conventional synthetic resin films, however, are much inferior to glass substrates in heat resistance or moisture resistance and thus unavoidably undergoes deformation, for example, in heating in the step of forming a metallic thin film by vapor deposition or the like, or in heating in the step of curing by heating after coating of a heat curable resin coating material, or unavoidably has poor chemical resistance, for example, undergoes deformation due to moisture absorption upon contact with an aqueous solution in the step of etching a metallic thin film or the step of developing a resist. The display or gas barrier film thus obtained suffers from problems with dimensional accuracy, for example, deteriorated flatness, delamination based on misregistration with the stacked metallic thin film, or deviation of dimension from the previously set dimension. Further, in displays such as LCDs and EL display panels, and organic electronic devices such as organic transistors, when the formed element comes into contact with moisture or oxygen, disadvantageously, performance is deteriorated, and troubles such as luminescence failure and circuit drive failure take place.
Accordingly, gas barrier films for use in display substrates, organic electronic device substrates, and displays are required to have the following properties: heat resistance of 150° C. or above and a coefficient of linear expansion of not more than 50 ppm for enhancing dimensional stability to a level that, for example, upon exposure to heat generated during processing or use or tension during heating, is less likely to cause deteriorated flatness and separation and is further less likely to cause elongation or deflection; and a ultrahigh level of gas barrier properties for avoiding a deterioration in performance upon contact of the formed element with moisture, oxygen or the like particularly in displays such as LCDs and EL display panels.
Main applications of the gas barrier film according to the present invention are not particularly limited to the above display substrates and may be used in any application where heat resistance and gas barrier properties are required. Such applications include packaging materials such as foods and pharmaceutical preparations, as well as touch panels, illumination film substrates, solar cell film substrates, circuit board film substrates, electronic papers, organic electronic devices such as organic transistors and the like.
A conventional gas barrier laminated film comprises a polymeric resin base material and a gas barrier film having a two-layer structure provided on the polymeric resin base material. The gas barrier film comprises two layers of an inorganic compound vapor deposited layer and a coating layer formed from a coating agent composed mainly of a water/alcohol mixed solution (see, for example, Japanese Patent Laid-Open No. 164591/1995).
Another conventional gas barrier laminated film comprises a polymeric resin base material and two layers provided on the polymeric resin base material. These two layers are an inorganic compound vapor deposited layer, and a coating layer formed from a coating agent comprising, as a main agent, a mixed solution composed of at least one metal alkoxide or its hydrolyzate and an isocyanate compound containing two or more isocyanate groups in its molecule and preferably containing a tin chloride, melamine, melamine resin, and formaldehyde (see, for example, Japanese Patent Laid-Open No. 268115/1995).
Further, the formation of a gas shielding layer on a transparent heat resistant base material by sputtering is also known (see, for example, Japanese Patent Laid-Open No. 222508/1999).
The films disclosed in all the above patent documents have water resistance and moisture resistance, have flexibility on a level that can withstand a certain level of deformation, and have gas barrier properties, but on the other hand, as described in the working examples, the oxygen permeability is about 1 cc/m2·day·atm, and, at best, the water vapor permeability and the oxygen permeability are 0.1 g/m2·day and about 0.3 cc/m2·day·atm, respectively. Thus, these films are disadvantageously unsatisfactory for preventing deterioration of luminescent layers or the like, for example, in organic EL elements. Further, the above patent documents neither describe nor refer to heat resistance on a level of 150° C. or above, chemical resistance, and a low coefficient of linear expansion.